JP2002154416A - Method for varying friction coefficient especially in friction brake, and friction brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method allowing a speedy and reliable operation, by improving a method for varying a friction coefficient between two mutually frictionally engaging surfaces, especially between two working faces of a friction brake. SOLUTION: Gas in a high pressure is jetted into a gap between both working faces 20 and 21 to form a gas film between both working faces 20 and 21, and the gas film affects an effective friction coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for changing the coefficient of friction between two surfaces in frictional engagement with each other, in particular between two working surfaces of a friction brake, and a friction brake. At least one first working surface provided on the movable part to be braked, a second working surface provided on a part immovable with respect to the direction of movement of the part to be braked, and a working surface And an operating device for causing the brake devices to engage with each other in accordance with a desired braking action.

[0002]

BACKGROUND OF THE INVENTION In brakes, clutches and other devices in which two surfaces are frictionally engaged with each other to form a frictional connection between two components, the coefficient of friction FR is the normal force which presses both surfaces together. It is obtained from Fn and the coefficient of friction μ by the following equation.

[0003] Brake systems based on friction, for example friction brakes such as those used in motor vehicles, are generally provided with brake pads, which brake pads have one of two working surfaces engaged with one another. Formed and this brake pad serves as a wear part. In this case, the role of the brake pads is to make the value of the wear coefficient in contact with the opposite running surface of the brake disc or brake drum as constant as possible.

The adjustment of the desired braking action is achieved by generating a corresponding normal force, generally by hydraulic pressure in the braking system. In that case, the hydraulic pressure is generated by a master brake cylinder operated via a brake pedal and transmitted to the individual wheel brake cylinders via appropriate brake conduits, the pistons of the wheel brake cylinders connecting the respective brake pads. Crimping to the corresponding opposing running surface.

[0005] To prevent the wheels from locking during braking of the motor vehicle, the hydraulic pressure transmitted from the master brake cylinder to the wheel brake cylinders is varied by an anti-lock system.

In electromechanically operated friction brakes, in other words in the case of a type of friction brake in which the normal force for pressing the working surfaces against one another is generated by an electromechanical converter, for example an electric motor, the respective normal force acts to reduce the braking effect. Is not mitigated as quickly as with hydraulically actuated brakes, so that the anti-lock system operates as quickly and reliably with electromechanical brakes as with hydraulic brakes The problem of not doing so is compounded.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems.

[0008]

This object is achieved, according to the method of the invention, in that, as described in claim 1, between two surfaces which are in frictional engagement with each other, in particular the two of a friction brake. In a method for changing the coefficient of friction between working surfaces, a gas under high pressure is blown between both working surfaces to form a gas film between both working surfaces, and this gas film is more effective. Solved by affecting the coefficient of friction.

[0009]

The advantage of the method according to the invention for changing the coefficient of friction over the prior art is that a thin gas film is formed between the friction couples, in particular between the working surfaces of the friction brake. In this way, the frictional forces between the working surfaces are changed and are, in particular, reduced, so that the frictional connection and, consequently, the braking action are changed and, in particular, reduced. Therefore, an additional controller output results, which influences the frictional connection and thus the braking effect in an appropriate manner. Particularly in friction brakes in which the change in normal force takes place relatively slowly, a rapid change in the braking action is obtained via a change in the coefficient of friction.

[0010] In order to keep the coefficient of friction spatially constant over the mating surfaces when the coefficient of friction changes, the gas under high pressure for the formation of a gas film is simultaneously applied between the two surfaces at a plurality of points. It is particularly advantageous to be blown into. In this case, it is particularly advantageous if a plurality of points for blowing gas under high pressure are evenly distributed over the engagement area on both surfaces.

A further advantageous feature of the invention is characterized in that the pressure of the gas under high pressure is increased in the central part of the area in which the gas is blown in at a central part of the area outside the engagement area. Are distributed over the engagement area on both sides.

By using a plurality of distributed points for blowing gas under high pressure, even if both working surfaces engaging with each other are in uniform contact with each other over a large area, The desired gas film is obtained between the two working surfaces.

It is advantageous if the blowing pressure is adjustable so that the formation of the gas film and thus the change in the coefficient of friction can be controlled as required.

Instead of, or in addition to, the adjustable blowing pressure, the gas under high pressure is provided by a pulse duration and a pulse frequency which can be adjusted depending on the desired change in the coefficient of friction. It is blown in a pulse. This results in very precise control of the gas film for changing the coefficient of friction.

An advantage of the friction brake with the features according to the characterizing feature of claim 8 is that high pressure is applied between the two working surfaces in the region of the two working surfaces which are in contact with each other within the engagement region. At the inlet, so that a gas film to be formed can be formed between the two engaging surfaces, starting from the inlet.

[0016] In a friction brake having two or more pairs of active surfaces, at least one air inlet is provided in each of the active surfaces of each of the active surface pairs, and the air inlet connects the conduit. Advantageously, it is connected to the pressure gas source via This has the advantage that the friction forces on both sides of the brake disc remain the same, even if the respective coefficients of friction change, so that no undesired stresses occur in the brake disc. Correspondingly, drum brakes prevent significant stresses that would occur if different normal forces between the individual brake pads and the brake drum were to be applied but different frictional forces were acting due to changes in the coefficient of friction. You.

A large number of air inlets, each of which is evenly distributed and arranged, are provided in one of the working surfaces,
In this case, it is advantageous if these inlets are connected via a pressure line to a pressure distribution chamber which is connected to a source of pressurized gas. As a result, the pressure supplied from the source of pressure gas is supplied uniformly to the individual inlets, so that the coefficient of friction is varied uniformly over the area of engagement.

[0018] Each of the plurality of blow-off ports is provided on one of the working surfaces, and the blow-out ports are distributed so that the density of the blow-out holes is higher in the central portion than in the region outside the corresponding working surface. It is also conceivable that they are arranged.

A blow-off port is provided in the second working surface which is formed by the free surface of the friction material body and which is immobile in relation to the movement to be damped, so that the friction material body together with the support plate If it can be pressed against the first working surface by means of the actuating device, a simple construction of the friction brake is obtained, in which case the pressure distribution chamber, which is preferably connected to a source of pressurized gas, has a support plate for the body of friction material. Is placed within.

In order to be able to control the change in the coefficient of friction, in other words the formation of a gas film between the working surfaces, in a particularly simple manner, one or more inlets or distribution chambers and a pressure gas source are connected. In between, a valve device controlled by the braking force control device is provided. In this case, the valve device
The connection between the pressure gas source and the pressure distribution chamber or the inlet or outlets is opened and closed with an opening duration and a switching frequency which are adjusted depending on the desired change in the coefficient of friction. Can be controlled.

In short, the present invention has a different format from the prior art,
In one aspect, there is provided a method for reducing the braking effect, which allows a reduction in the number of components of the braking system. On the other hand, the invention also allows for an improved control and / or regulation method for the braking action when incorporated for braking pressure reduction in combination with conventional methods.

In particular, in the case of electromechanically operated friction brakes in which the normal force acting on the working surfaces in frictional engagement with one another cannot be rapidly reduced, the present invention provides a rapidly responsive antilock control.

[0023]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to an illustrated embodiment. Corresponding parts are designated by the same reference numerals in the various figures of the drawings.

FIG. 1 shows an example for a friction brake,
One brake disc 10 and two brake shoes 11
And a brake shoe is disposed on the caliper 12 (not shown in detail). The piston 13 of the wheel brake cylinder 14 is connected to the master brake cylinder via a brake line 15 in a manner not shown, so that one of the brake shoes 11 can be directly connected to the brake disk 10 during braking.
And crimp it. The other brake shoe 11 is pressed against the brake disc 10 by a leg of the caliper 12 located on the other side of the brake disc 10. This is because not only does the piston 13 move toward the corresponding brake shoe 11 when the wheel brake cylinder 14 is operated, but at the same time the caliper 12 also moves in the opposite direction, that is to the right in FIG. Is applied to the brake disk 10 with the same force.

The two brake shoes 11 each have a brake pad 16 as a body of friction material, which is mounted on a back plate 17 which serves as a support plate.

As can be seen in particular from FIGS. 2 and 3, a number of passages 18 are provided in the brake pads 16 of the respective brake shoes 11 and these passages extend completely through the brake pads 16 and Opened in the mouth 19, these blow openings are provided in a friction or working surface 21 which engages the corresponding opposing running surface 20 of the brake disc 10. A pressure distribution chamber 22 is formed in the back plate 17 and is connected to a pressure gas source 24 via a pressure conduit 23 and on the other side via a passage 25 to the passage 18 and thus to the inlet 19. ing.

The inlets 19 in the friction or working surface 21 of the brake pad 16 can be distributed regularly over the brake pad 16 as shown in the drawing, and can have a uniform mutual spacing. . However, in the central part of the working surface 21, the inlet 19
It is also possible to arrange the blow-out ports 19 in the working surface 21 in a distributed manner so as to increase the density of the blow-off holes. In that case, for example, it is possible that the spacing between one blow-in port 19 and a plurality of blow-in ports 19 immediately adjacent thereto is the same. However, as shown in FIG. 2, the relative movement direction R between the brake shoe 11 and the brake disc 10 is also shown.
It is also conceivable that the interval between the blow-out ports 19 in the direction perpendicular to the direction of the horizontal direction is smaller than the mutual gap between the blow-out ports 19 in the direction of the relative movement R. The optimal distribution of the inlet 19 can be calculated by careful consideration of the pattern or can be known by appropriate experimentation.

A valve device 26 is provided in the pressure conduit 23 and can be controlled by a braking force control device 27 in the same manner as the pressure gas source 24.

During braking, the normally open air inlet 19
Is closed by the corresponding opposing running surface 20 of the brake disc 10, and the brake pad 16 is pressed against the brake disc 10 at its frictional or working surface 21. When it is recognized by the braking force control device 27 during braking that it is necessary to reduce the braking effect when the wheel is locked, and that the so-called “anti-lock” is necessary, the pressure gas source 24 and the valve device 26 of the braking force control device 27 are connected. As a result, the gas under high pressure, such as air, is supplied to the pressure distribution chamber 22 in the back plate 17 via the pressure conduit 23. As a result, the pressure propagates to the blow-in port 19, and gas under high pressure is blown between the mutually engaged surfaces of the brake pad 16 and the brake disk 10. As a result, a gas film is formed between the surfaces engaged with each other, that is, between the opposing running surface 20 and the working surface 21, and this gas film reduces the coefficient of friction between both friction pairs, and thus the frictional force. , Which results in a reduction in the braking force.

As soon as the braking action is required again, the connection between the pressure gas source 24 and the pressure distribution chamber 22 is interrupted by the valve device 26, so that the gas film between the friction couple quickly disappears. However, the coefficient of friction rises again to its original value, so that a high frictional force level is again formed.

In this case, in particular, the pressure supplied by the pressure gas source can be adjusted depending on the desired friction coefficient reduction so that the friction coefficient reduction can be carried out appropriately.
In order to slightly reduce the coefficient of friction between the friction surface or working surface 21 of the brake pad 16 and the opposing running surface of the brake disc 10, it is sufficient to apply a gas pressure slightly lower than the brake pressure. Increasing the gas pressure further promotes the formation of a gas film to reduce the coefficient of friction, which can greatly change the coefficient of friction.

If the valve device 26 is operated by the braking force control device 27 so that the connection between the pressure gas source and the inlet 19 is quickly opened and closed alternately, a constant level of gas pressure is supplied. Depending on the pressure gas source used, different degrees of change of the coefficient of friction are obtained. This causes the gas film to increase to a certain value during the opening time of the valve device 26, and then, while the valve device 26 is closed, this value is again reduced or distributed to a certain degree. Therefore, the gas film is increased again at the subsequent opening. Since the opening and closing of the valve device 26 is rapidly and alternately performed, the equilibrium gas film that allows a defined reduction in the coefficient of friction is adjusted during the friction couple. By varying the ratio between open and closed, more or less varying degrees of gas film change are properly controlled.

Furthermore, if the passages 18 and 25 for connecting the blow-off port 19 and the corresponding pressure distribution chamber 22 are appropriately formed, the opening and closing of the valve device 26 are alternately performed, even though the opening and closing are alternately performed. It is also possible to generate a constant pressure depending on the ratio between the pressure and the closure. This is because the pressure distribution chamber 22 serves as a kind of pressure transition smooth cushion.

However, the present invention goes beyond merely enabling the responsive behavior of an antilock system to be improved.
Braking noise and other effects that impair braking comfort can also be reduced.

Most problems of this kind begin at the point of friction between the respective friction couples, that is to say between the friction or working surface 21 of the brake pad 16 and the opposite running surface of the brake disc 10 in the embodiment shown. Has in frictional contact. Under certain braking conditions, unstable conditions occur that can cause significant vibrational excitations in the individual parts of the brake. An important point in this case is the transition from static friction to sliding friction. By slightly reducing the coefficient of friction, noise can be effectively suppressed, especially in the transition between static friction and sliding friction.

For example, first, the occurrence of braking friction noise can be detected by a suitable sensor, for example, a microphone, an acceleration sensor, or the like. Then, as soon as the braking friction noise is detected, gas under high pressure is appropriately supplied to the blow-in port 19. By providing a very small gas film between the friction couple by feeding, and by eliminating the braking friction noise by changing the coefficient of friction between the friction couple by this gas film, by secondary means. It is possible to further suppress the braking friction noise whose generation is already reduced.

The sudden change in braking effect, especially as a result of the sudden transition from static friction to sliding friction, especially when starting up from a state in which the brakes are still partially actuated, also results in the brake pad 16 The gas film is formed between the working surfaces of the brake disk 10 and the brake disk 10 which are engaged with each other, so that the pressure is reduced.

The invention applies not only to disc brakes but also to drum brakes and other friction brakes. Furthermore, in the friction clutch, connection and disengagement are facilitated by the gas film formed between the friction couple of the clutch, and the friction at the same time is equalized, so that the friction couple has a small wear and, consequently, the relatively long length of the clutch. It is also possible to obtain a useful life.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a friction brake according to the present invention in a partially sectional view.

FIG. 2 is a plan view of a brake shoe of the friction brake according to the present invention.

FIG. 3 is a sectional view of the brake shoe taken along line III-III in FIG. 2;

[Description of Signs] 10 brake discs, 11 brake shoes,
12 caliper, 13 piston, 14 wheel brake cylinder, 15 brake conduit, 16 brake pad, 17 back plate (support plate), 1
8 passage, 19 air inlet, 20 opposing running surface, 21
Working surface, 22 pressure distribution chamber, 23 pressure conduit, 2
4 pressure gas source, 25 passage, 26 valve device, 2
7 braking force control device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F16D 65/847 F16D 65/847 F term (reference) 3D046 BB21 BB28 EE01 LL14 3J058 AA48 AA53 AA62 AA77 AA87 BA14 BA76 CA43 CA78 CD03 FA01 GA92

Claims (17)

[Claims] 2. The method according to claim 1, wherein the two surfaces are in frictional engagement with each other.
0,21), in particular a method for changing the coefficient of friction between the two working surfaces (20, 21) of the friction brake, wherein a gas under high pressure is applied to both working surfaces (20, 21). Blowing between them to form a gas film between the two working surfaces (20, 21), wherein the gas film influences the effective coefficient of friction, for changing the coefficient of friction. Method. 2. A method according to claim 1, wherein the gas under high pressure is supplied to a plurality of locations.
2. The method according to claim 1, wherein the air is blown simultaneously between the two working surfaces (20, 21). 3. The device according to claim 2, wherein the plurality of points for injecting gas under high pressure are distributed evenly over the area of engagement of the two working surfaces. the method of. 4. A plurality of said gas injecting gas under high pressure so that the density of the location (19) for injecting gas under high pressure is higher in the center of the engagement area than in the outer area. 3. The method according to claim 2, wherein the points are distributed over the points of engagement of the two working surfaces. 5. The method as claimed in claim 1, wherein the injection pressure of the gas under high pressure is adjusted as a function of a desired change in the coefficient of friction. 6. The method according to claim 1, wherein the gas under high pressure is pulsed with a pulse duration and a pulse frequency which can be adjusted depending on the desired change in the coefficient of friction. Method. 7. The method according to claim 1, wherein a gas under high pressure for changing the coefficient of friction is continuously blown between the two working surfaces. . 8. A friction brake, wherein at least one first working surface provided on the movable part (10) to be braked and a direction of movement of the part (10) to be braked. An operating device (13, 1) for braking the second working surface (21) provided on the stationary part (11) and the working surfaces (20, 21) to each other according to a desired braking action;
4), and one of the working surfaces (20, 2)
Within 1) there is provided at least one inlet (19) which is connected via a conduit (23) to a source of pressurized gas (24), so that the coefficient of friction of the working surface pair is changed. The gas under high pressure is transferred to both working surfaces (20, 2).
A friction brake characterized in that it can be blown during 1). 9. When there are two or more working surface pairs, at least one air inlet (19) is provided in one of the working surfaces (21) of each of the working surface pairs, 9. A friction brake according to claim 8, wherein said inlet is connected to a source of pressurized gas (24) via a conduit (23). 10. A plurality of air inlets (19), each of which is uniformly distributed, is provided on one of the working surfaces (21).
The friction brake according to claim 8, wherein the friction brake is provided on the friction brake. 11. A plurality of air inlets (19) each being provided on one of the working surfaces (21), said working surface (21) being more central than the outer region of the corresponding working surface. 10. The friction brake according to claim 8, wherein the friction brakes are distributed and arranged so that the density of the air inlets is high. 12. The pressure distributing chamber (22) having an inlet (19).
10. A friction brake according to claim 9, wherein the pressure distribution chamber is connected to a source of pressurized gas (24) via a pressure conduit (23). 13. The method according to claim 8, wherein the air inlet is provided on a second working surface which is stationary in relation to the movement to be braked. Friction brake. 14. A second working surface (21), which is immobile in relation to the movement to be damped, is formed by the free surface of the friction material body (16), which friction material body (16)
14. The first working surface (20) can be crimped together with the support plate (17) by the operating device (13, 14).
The described friction brake. 15. A pressure distribution chamber (22) coupled to a source of pressurized gas (24) comprises a support plate (1) for a friction material body (16).
The friction brake according to claim 12, wherein the friction brake is arranged in 7). 16. A valve device (26) controlled by a braking force control device (27) between one or more inlets (19) or pressure distribution chambers (22) and a pressure gas source (24). The friction brake according to any one of claims 8 to 14, wherein the friction brake is provided. 17. The valve device (26) is controllable so that the connection between the source of pressure gas (24) and the pressure distribution chamber (22) or the inlet or outlets (19) is frictionally 17. The friction brake according to claim 16, wherein the brake is opened and closed with an opening duration and a switching frequency that are adjusted depending on a desired change in the coefficient.